What is the working principle of pneumatic control valve?

Pneumatic control valve is one of the industrial process control instruments widely used in petroleum, chemical industry, electric power, metallurgy and other industrial enterprises. In chemical production, the regulating valve is essential in the regulating system. It is an important part of industrial automation system, just like the hands and feet of production process automation. Next, Shanghai Tiger Fish, a professional valve maker, will show you a comprehensive understanding of pneumatic control valves.

Pneumatic control valve takes compressed air as power source and cylinder as actuator, and drives the valve to realize on-off or proportional adjustment with the help of electric valve positioner, converter, solenoid valve, position maintaining valve and other accessories, and receives the control signal of industrial automation control system to complete the adjustment of various process parameters such as flow, pressure and temperature of pipeline medium. Pneumatic control valve is characterized by simple control, rapid response, intrinsic safety and no need for additional explosion-proof measures.

Pneumatic control valve is usually composed of pneumatic actuator and control valve connected, installed and debugged. Pneumatic actuators can be divided into single-acting and double-acting types. There is a return spring in single-acting actuator, but there is no return spring in double-acting actuator. Among them, the single-acting actuator can automatically return to the initial open or closed state of the valve when it loses its origin or suddenly fails.

According to the action form, pneumatic control valves can be divided into two types, namely, the so-called normally open type and the normally closed type. The air opening or closing of Shanghai-Chongqing pneumatic control valve is usually realized by the positive and negative actions of the actuator and the different assembly methods of the valve structure.

Action mode of pneumatic control valve

Air-open (normally closed) means that when the air pressure on the membrane head increases, the valve moves in the direction of increasing opening, and when the upper limit of input air pressure is reached, the valve is fully opened. On the contrary, when the air pressure decreases, the valve moves in the closing direction, and when there is no air input, the valve is completely closed.

The movement direction of air-closed type (normally open type) is opposite to that of air-opened type. When the air pressure increases, the valve moves in the closing direction; When the air pressure decreases or does not decrease, the valve will be opened or fully opened.

The selection of gas switch is based on the safety of process production. When the air supply is cut off, it is safe whether the regulating valve is in the closed position or the open position.

valve positioner

Valve positioner is the main accessory of control valve, and it is widely used with Shanghai-Chongqing pneumatic control valve. It receives the output signal of the regulator, and then controls the pneumatic regulating valve with its output signal. When the regulating valve acts, the displacement of the valve stem is fed back to the valve positioner through the mechanical device, and the valve position is transmitted to the upper system through the electrical signal. Valve positioner can be divided into pneumatic valve positioner, electro-pneumatic valve positioner and intelligent valve positioner according to its structure and working principle.

The invention can increase the output power of the regulating valve, reduce the transmission lag of the regulating signal, accelerate the moving speed of the valve stem, improve the linearity of the valve, overcome the friction of the valve stem and eliminate the influence of unbalanced force, thus ensuring the correct positioning of the regulating valve.

Actuator can be divided into pneumatic actuator and electric actuator, and can also be divided into straight stroke and angular stroke. Used for automatically and manually opening and closing various cutting doors, wind shields, etc.